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I was trying to replace a few electrical outlets around the house with new tamper-resistant ones. When I pulled one of the outlets out of the box, I noticed that 1) there was no ground wire anywhere, 2) two white wires were under the same screw and one single black wire on the other side. This was a non-GFCI outlet in the kitchen.

I tried another outlet in the living room and in this case there were two hot wires under the same screw and two white wires under another screw on the other side of the outlet. Before I turned off the power, I had tested both outlets with a receptacle tester that showed they were correctly wired.

Is there a reason why these wires were connected to the same terminal? Should I replicate the same arrangement when installing the new outlets? Or should I put these wires under different screws?

  • Can you post photos of the insides of the boxes in question? – ThreePhaseEel Aug 30 '17 at 11:39
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The NEC now prefers you use the pigtail method.Here's a quick image to help. enter image description here

  • With a pigtail you can disconnect the outlet without disrupting downstream circuits. Otherwise, not. In general it is always a better practice to use pigtails unless the device you are connecting (outlet, light) is at the end of a run. – mickeyf Aug 30 '17 at 12:56
  • Nowhere on the NEC does it "prefer" anything. It says "shall" when it is required or "shall be permitted" when you are allowed to do it. Nowhere in the Code does it require a hot wire to be pigtailed. Only Multiwire Branch Circuits require the pigtail of a neutral. The Code requires the ground to be pigtailed only if you don't have self grounding receptacles so the receptacle can't interrupt the ground circuit. – ArchonOSX Aug 30 '17 at 20:31
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You can replace the receptacles exactly as you found them. Putting both wires under one screw is just a matter of convenience.

Some people like to pigtail the receptacles by making a joint with the wires and a pigtail to the receptacle. This is not required by the Code in your case, just a choice by the installer, but it requires more material and labor.

If you have metal boxes, one of the old ways to ground a metal box was to wrap the ground wire around the cable inserted into the cable clamp in the back of the box. So, your tester will show everything is fine even though you can't find a ground wire.

In this case, it is imperitive you replace the receptacles with self-grounding type receptacles. These have a metal clip on one of the screws on the receptacle. The other option is to use a ground screw or a box clip to attach a ground wire to the metal box and terminate that on the ground screw of the receptacle.

Good luck and stay safe!

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    How does one effectively put two wires under one screw? I thought this was illegal, and I've always found it unsatisfactory, as one tends to jump out. – isherwood Aug 30 '17 at 13:46
  • I think there are modern high quality duplex receptacles which have side screws which can secure wires looped around the screw and which also secure wires in back holes with screw pressure. As I understand it one could attach as many as four wires and maybe six hot and the same number of neutrals. I wonder how this is possible for a side loop and back insertion to both be tight, but this seems to be allowed. – Jim Stewart Aug 30 '17 at 14:44
  • The clamps on some receptacles allow one wire in each side. Usually these are a better grade receptacle. The cheap ones only have a screw with plastic shoulders. – ArchonOSX Aug 30 '17 at 15:53
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    This duplex receptacle looks like four wires per side could be connected: homedepot.com/p/… – Jim Stewart Aug 30 '17 at 18:45

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